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This multicenter, international, Phase Ib/II trial consists of two stages: a Phase Ib, open-label stage in which the recommended Phase II dose will be determined for ipatasertib and apitolisib in combination with abiraterone and prednisone/prednisolone and a Phase II, 3-arm, double-blind, randomized comparison of ipatasertib with abiraterone and prednisone/prednisolone versus placebo with abiraterone and prednisone/prednisolone.

Phase II: Percentage of Participants Who Died - ITT Population [ Time Frame: Screening up to death (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Overall Survival - ITT Population [ Time Frame: Screening up to death (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants Who Died in Participants With ICR PTEN Loss [ Time Frame: Screening up to death (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Overall Survival in Participants With ICR PTEN Loss [ Time Frame: Screening up to death (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants With Prostate-Specific Antigen (PSA) Progression (as Assessed by Prostate Cancer Working Group 2 Criteria) - ITT Population [ Time Frame: Screening up to PSA progression (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Time to PSA Progression (as Assessed by Prostate Cancer Working Group 2 Criteria) - ITT Population [ Time Frame: Screening up to PSA progression (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants With PSA Progression (as Assessed by Prostate Cancer Working Group 2 Criteria) in Participants With ICR PTEN Loss [ Time Frame: Screening up to PSA progression (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Time to PSA Progression (as Assessed by Prostate Cancer Working Group 2 Criteria) in Participants With ICR PTEN Loss [ Time Frame: Screening up to PSA progression (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants With Objective Response as Assessed by RECIST 1.1 - ITT Population [ Time Frame: Screening up to radiographic progression or death, whichever occurred first (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants With Objective Response (as Assessed by RECIST 1.1) in Participants With ICR PTEN Loss [ Time Frame: Screening up to radiographic progression or death, whichever occurred first (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Duration of Tumor Response, as Assessed by RECIST 1.1 - ITT Population [ Time Frame: Screening up to radiographic progression or death, whichever occurred first (assessed at screening, after Cycles 3, 5, 7, 9, every three cycles [12 weeks] thereafter up to end of treatment [up to 3.6 years overall]) (cycle length = 28 days) ]

Phase II: Percentage of Participants With Circulating Tumor Cells (CTC) Reduction Response - ITT Population [ Time Frame: Screening, on Day 1 of Cycle 2, on Day 1 of Cycle 3, and at the treatment completion visit (up to overall 3.6 years) (cycle length=28 days) ]

Phase II: Percentage of Participants With CTC Reduction Response in Participants With ICR PTEN Loss [ Time Frame: Baseline, on Day 1 of Cycle 2, on Day 1 of Cycle 3, and at the treatment completion visit (up to overall 3.6 years) (cycle length=28 days) ]

Phase II: Percentage of Participants With CTC Conversion - ITT Population [ Time Frame: Baseline, on Day 1 of Cycle 2, on Day 1 of Cycle 3, and at the treatment completion visit (up to overall 3.6 years) (cycle length=28 days) ]

Phase II: Percentage of Participants With CTC Conversion in Participants With ICR PTEN Loss [ Time Frame: Baseline, on Day 1 of Cycle 2, on Day 1 of Cycle 3, and at the treatment completion visit (up to overall 3.6 years) (cycle length=28 days) ]

Phase II: Percentage of Participants With Pain Progression - ITT Population [ Time Frame: Screening, Day 1 of each cycle (cycle length=28 days) up to treatment completion (up to 3.6 years) ]

Phase II: Time to Pain Progression - ITT Population [ Time Frame: Screening, Day 1 of each cycle (cycle length=28 days) up to treatment completion (up to 3.6 years) ]

Phase II: Percentage of Participants With Pain Progression in Participants With ICR PTEN Loss [ Time Frame: Screening, Day 1 of each cycle (cycle length=28 days) up to treatment completion (up to 3.6 years) ]

Phase II: Time to Pain Progression in Participants With ICR PTEN Loss [ Time Frame: Screening, Day 1 of each cycle (cycle length=28 days) up to treatment completion (up to 3.6 years) ]

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Ages Eligible for Study:

18 Years and older (Adult, Senior)

Sexes Eligible for Study:

Male

Accepts Healthy Volunteers:

No

Criteria

Inclusion Criteria:

Histologically confirmed metastatic or advanced prostate adenocarcinoma that has been previously treated with docetaxel-based therapy and has progressed during treatment of at least one hormonal therapy